I have used ATF for years, it works great. Here is a clip from Grant Cunningham on gun oils:

Quote:

Cut to the chase! What should I use?
Let's start with oil. Most people use oils that are way too heavy; thicker is not better! Use a relatively thin oil with the correct properties, and use it very sparingly - most "oil failures" I've seen have been from too much, rather than too little, oil.

Frankly, in terms of mechanical performance, most oils "work"; some are better than others, but everything will make parts move for a while. The weakest area of most oils is in corrosion resistance - and on a gun, corrosion is a bad thing! There have been lots of claims, but those people who have actually taken the time to run experiments to test corrosion on steel have found that the products with the greatest hype are often the worst at corrosion resistance. Not surprisingly, plain mineral oils, such as Rem Oil, score at the very bottom of the list.

One product that scores pretty well in corrosion testing is also the readily available and dirt cheap. It also has good migration, a good boundary lubrication package, is the right weight (thickness) for general firearms use, doesn't oxidize over long periods of storage, and is compatible with a wide range of metals and plastics. In addition, it is recommended by at least one real degreed firearms engineer! Just what is this miracle elixir??

Dexron-type Automatic Transmission Fluid (ATF). That's right, plain ol' ATF. The kind you get at every gas station, auto parts store, and even most convenience stores. Synthetic or regular, either will work just fine. ATF is not perfect, however; it does have a slight odor to it, the red dye used to differentiate it from motor oil will stain, and it’s not non-toxic. If you find those attributes objectionable, a decent alternative that is still readily available is "NyOil." Check your local auto parts store, in the aisle where they keep the miscellaneous lubricants and additives.)

If we were to spec out a "best in class" oil, it would be one made for lubricating food processing machiner, like Lubriplate's FMO-AW oil (specifically the 350-AW weight.) Food grade lubricants have to prevent wear in sometimes corrosive environments and they have to do so even after being wiped off of the surface they’re protecting! They have good boundary protection and very high corrosion resistance especially in the presence of acids, alkalis, and moisture. They’re darned near tailor-made for our use!